Positioning a cursor on the display screen of a computer

ABSTRACT

A computer system comprises a keyboard ( 11 ), a display screen ( 13 ), a first pair of position-sensing electrodes ( 18.1, 18.2 ), a second pair of position-sensing electrodes ( 20.1, 20.2 ), a signal injection electrode ( 22 ), and an oscillator ( 27 ). The oscillator injects a signal via the signal injection electrode and the operator&#39;s left hand (L) into the operator&#39;s body, and this creates a field around the operator&#39;s right hand (R). The position-sensing electrodes are arranged underneath the keyboard and sense the strength of the field. This enables the position of the operator&#39;s right hand (R) in an X-Y plane above the keyboard to be determined. To this end the position-sensitive electrodes are connected via synchronous detectors ( 34, 44 ) and an analogue-to-digital converter ( 36 ) to a microprocessor ( 46 ), which operates to control the position of a cursor on the display screen.

[0001] This application is a continuation of PCT/IB99/00579 filed Apr.6, 1999, which claims priority from South African patent application98/2910 filed Apr. 6, 1998.

[0002] This invention relates to a method of positioning a cursor on thedisplay screen of a computer, under control of an operator, and to meansfor carrying out the method.

[0003] The term “cursor” is to be understood as encompassing a pointeror other device or symbol that is displayed on the display screen of acomputer and can be moved about on the screen under control of theoperator. A cursor could, for example, be used to point at or designatean icon or attribute displayed on the display screen and that is to beselected.

[0004] According to the invention there is provided a method ofpositioning a cursor on the display screen of a computer, under controlof an operator, the method comprising the steps of:

[0005] establishing a field about a movable body part of the operator;

[0006] sensing the strength of the field at one or more predeterminedpositions in a fixed reference frame, thereby to provide a controlvariable corresponding to the position of the body part in the referenceframe; and

[0007] positioning the cursor on the display screen in response to thecontrol variable.

[0008] The arrangement may then be such that the movable body part actsas a radiating antenna.

[0009] The movable body part may be one of the hands of the operator.

[0010] Where the movable body part is one of the hands of the operator,the field may be established by injecting an electrical signal into theoperator's body via the other hand of the operator.

[0011] The strength of the field may be sensed by means of a first pairof position-sensing electrodes spaced apart in a first direction in thereference frame, to provide a first control variable corresponding tothe position of the body part in the first direction, and a second pairof position-sensing electrodes spaced apart in a second directionperpendicular to the first direction, to provide a second controlvariable corresponding to the position of the body part in the seconddirection.

[0012] The term “electrode” is to be interpreted in a broad sense so asto include also an antenna.

[0013] The cursor may be positioned by moving it to a position on thedisplay screen corresponding to the position of the body part in thereference frame, if the body part is within an imaginary boundary in thereference frame, and by continuing to mo%ee it along a linecorresponding to the direction in which the body part approached theboundary, if the body part is at or beyond the boundary.

[0014] Further according to the invention there is provided a computersystem which comprises a display screen, a keyboard for entry of datainto the system, and positioning means for controlling the position of acursor on the display screen, the positioning means comprising:

[0015] position-sensing electrodes placed in a fixed reference frame,for sensing the strength of a field established about a movable bodypart of an operator and thereby to provide a control variablecorresponding to the position of the body part in the reference frame;and

[0016] control means operative in response to the control variable toposition the cursor on the display screen in accordance with theposition of the body part in the reference frame.

[0017] Where said body part is one of the hands of the operator, theposition-sensing electrodes may be so arranged with respect to thekeyboard that the operator can control the position of the cursor bymoving said hand in a hovering manner over the keyboard.

[0018] The system may further comprise a signal generator for generatingan alternating electrical signal, and an injection electrode forinjecting the electrical signal into the body of the operator and soestablish the electrical field about said movable body part. Where saidmovable body part is one of the hands of the operator, the injectionelectrode may be arranged to inject the electrical signal into the bodyof the operator via the other hand of the operator.

[0019] The system may further comprise one or more click switches foroperation by the operator. The click switch or switches may be arrangedto be operated by said other hand of the operator.

[0020] The system may further comprise a conventional pointing device,and selection means for enabling the operator to select the conventionalpointing device for controlling the position of the cursor on thedisplay screen.

[0021] The invention extends to an accessory for use in positioning acursor on the display screen of a computer, under control of anoperator, the accessory comprising:

[0022] signal generating means for generating an electrical signal;

[0023] an injection electrode coupled to the signal generating means,for injecting the electrical signal into the body of the operator,thereby to establish a field about a movable body part of the operator;

[0024] position-sensing electrodes for placement in a fixed referenceframe, for sensing the strength of the electrical field; and

[0025] means coupled to the position-sensing electrodes for generating acontrol variable corresponding to the position of the body part in thereference frame, whereby the cursor can be positioned in response to thecontrol variable.

[0026] The invention will now be described in more detail, by way ofexample, with reference to the accompanying diagrammatic drawings.

[0027] In the drawings:

[0028]FIG. 1 illustrates a computer system according to a firstembodiment of the invention; and

[0029]FIG. 2 illustrates a computer system according to a secondembodiment of the invention.

[0030] Referring first to FIG. 1 , reference numeral 10.1 generallydesignates a computer system comprising a personal computer (PC) of theportable or desk-top type. The PC comprises various components includinga keyboard 11, a microprocessor, memory, and disc drives housed in acabinet 12, a display device or monitor 13, and a pointing device in theform of a mouse 14. These can all be of the conventional type. Inaccordance with the invention, the computer system is further providedwith an accessory 15 for use in controlling the PC, and moreparticularly the position of a cursor on the monitor 13. The keyboard 11is connected to the rest of the PC in a conventional manner. The mouse14 is connected to the rest of the PC via the accessory 15, in a mannerthat will be described in more detail hereinafter,

[0031] The accessory 15 may be provided in a form in which it canreadily be retrofitted to an existing, conventional PC. Thus, it maycomprise a panel 16 which can be placed under the keyboard 11. On thepanel 16 there are two pairs of spaced position-sensing electrodes,namely a first pair of electrodes 18.1 and 18.2, and a second pair ofelectrodes 20.1 and 20.2. The electrodes 18.1 and 18.2 are spaced in anX co-ordinate direction, i.e. along the length of the keyboard, and, aswill be explained in more detail hereinafter, are thus able to detectthe position of the operator's right hand R in the X co-ordinatedirection. The electrodes 20.1 and 20.2 are spaced in the Y co-ordinatedirection, i.e. in a direction perpendicular to the X co-ordinatedirection, and are thus able to detect the position of the operator'sright hand R in the Y co-ordinate direction. Towards the left hand sidethereof the panel 16 is provided with a signal injection electrode 22and a pair of click switches 24 and 26. The click switches 24 and 26,and signal injection electrode 22 are so arranged that, when theoperator's left hand L is placed in position on the panel for operatingthe click switch 24 with the left thumb and the click switch 26 with oneof the other left hand fingers, i.e. as illustrated in the drawing, thepalm of the operator's left hand will be over the signal injectionelectrode 22.

[0032] It will be understood that the electrode pairs 18.1, 18.2 and20.1, 20.2, as well as the electrode 22 and the click switches 24 and 26can be made to form a built-in part of the keyboard 11. In this eventthe panel 16 can be omitted. It will also be understood 15 that furtherelectrode pairs in addition to the electrode pairs 18.1, 18.2 and 20.1,20.2 may be provided, so that the position of the right hand R in athird or Z co-ordinate direction, perpendicular to the X-Y plane, canalso be determined. It will further be understood that further clickswitches, in addition to the click switches 24 and 26, may be provided.

[0033] The accessory 15 further comprises an oscillator 27 which, inoperation, generates an electrical signal having a frequency of about 20kHz. The output of the oscillator 27 is coupled to the signal injectionelectrode 22.

[0034] The click switches 24, 26 can be of the type that requirephysical actuation, as in the case of the click switches of aconventional mouse.

[0035] The electrodes 18.1 and 18.2 are coupled to the two inputs,respectively, of a difference amplifier 28, each via a high impedancebuffer amplifier 30. The output of the difference amplifier 28 is fedvia a band-pass filter 32 and a synchronous detector 34 to a first ofthe inputs of an analogue-to-digital converter (ADC) 36. Likewise, theelectrodes 20.1 and 20.2 are connected to the two inputs, respectively,of a difference amplifier 38, each via a high impedance buffer amplifier40, and the output of the difference amplifier 38 is connected via aband-pass filter 42 and a synchronous detector 44 to a second input ofthe analogue-to digital converter 36. The band-pass filters 32 and 42each have a centre frequency which corresponds to the frequency of theoscillator 27.

[0036] The accessory 15 further comprises a microprocessor 46. Theoutput of the analogue-to-digital converter 36 is connected to an inputof the microprocessor 46. The click switches 24 and 26 are alsoconnected to inputs of the microprocessor 46. Likewise, the mouse 14 isconnected to an input of the microprocessor 46.

[0037] In one form of the invention the click switches 24, 26 areprovided with touch-sensitive electrodes, the arrangement being suchthat the microprocessor 46 is, via these touch-sensitive electrodes,able to detect whether or not the operator's left hand is in theposition illustrated in the drawing, i.e. in a position in which theoperator's left thumb and fingers touch the click switches 24, 26. Thisis the position that is required for the signal from the oscillator 27to be injected into the body of the operator via the signal injectionelectrode 22. It will be understood that the injection electrode 22 maybe provided on a click or pressure switch, in which event this click orpressure switch will have the same effect as the click switches 24, 26.

[0038] The microprocessor 46 has an output 48 which is connected to aserial port of the PC.

[0039] Operation of the System will Now be Described

[0040] When the operator's left hand L is in the position illustrated inthe drawing, the electrical signal generated by the oscillator 27 isinjected via the signal injection electrode 22 into the operator's body.The injection may be effected by conduction, in which event physicalcontact with the electrode 22 will be required, or it may be effected bymeans of capacitive, electromagnetic, or radiation induction, in whichevent physical contact with the electrode 22 is not required. Theinjected signal creates an alternating electric field around theoperator's body, including, via conduction through the operator's body,the operator's right hand R. The electrodes 18.1, 18.2 and 20.1, 20.2are able to detect the strength (i.e. amplitude) of this field and, fromthis determine the position of the operator's right hand in the X and Yco-ordinate directions. This is done in conjunction with the differenceamplifiers 28, 38 and the synchronous detectors 34, 44. Any extraneoussignals are filtered out by the band-pass filters 32, 42, and thesynchronous detectors 34, 44 provide analogue outputs corresponding tothe position of the operator's right hand in, respectively, the X and Yco-ordinate directions. The two analogue signals, one provided by thesynchronous detector 34 and the other by the synchronous detector 44,are fed to the analogue-to-digital converter 36, which converts the twosignals to a digital form. The microprocessor 46 serves to convert thesignal into a suitable data bit-stream. The protocol of the bit-streammay be such as to emulate a standard mouse protocol required by aconventional software mouse driver resident in the PC. The bit-stream isfed to a serial port of the PC via the output 48 and is interpreted bythe computer as if it was reading data sent by a conventional mouseduring normal mouse operation.

[0041] The information contained in the bit-stream could also betransmitted to the PC via an existing data link between the 30 keyboardand the PC, using suitable software.

[0042] The operator may operate the click switches 24, 26 in the samemanner as that in which the click switches of a conventional mouse areoperated.

[0043] While the operator's left hand L is in the position illustratedin the drawing, as detected by the touch sensitive electrodes on theswitches 24, 26 referred to above, the microprocessor 46 operates todisable the conventional mouse 14.

[0044] Should the operator want to use the conventional mouse I4, theoperator simply has to move his left hand away from the positionillustrated in the drawing. This will be detected by the microprocessor46 via the touch-sensitive electrodes on the click switches 24, 26, andcauses the microprocessor to disable the input received from theanalogue-to-digital converter 36 and, instead, switch over to the inputreceived from the mouse 14.

[0045] The system may also operate through other forms of energy inducedin the body of the operator, such as, for example, the 5 OHz normallyused for mains power and which will normally be induced in the body ofthe operator via cables and other electrical equipment in the vicinityof the operator, or by any other non-contact injector.

[0046] Referring now to FIG. 2, reference numeral 10.2 generallyindicates a computer system which is similar to the computer system10.1, the same reference numerals being used to indicate the same orsimilar parts. The system 10.2 differs from the system 10.1 as followshereunder.

[0047] First, the electrodes 18.1 and 18.2 are arranged so that they areboth on one side, in the X direction, of the operator's right hand R,and the electrodes 20.1 and 20.2 are arranged so that they are both onone side, in the Y direction, of the operator's right hand R. Thisarrangement has the advantage that it renders the system less sensitiveto electromagnetic noise and less sensitive to changes in the height ofthe operator's right hand above the keyboard 11, and that it is easierto implement physically than in the case of the electrode arrangementillustrated in FIG. 1.

[0048] Secondly, an analogue linearizer 50 is connected between theband-pass filter 32 and the synchronous detector 34. This is required tocompensate for the non-linearity introduced by the fact that theelectrodes 18.1 and 18.2 are both to one side of the operator's righthand instead of being on opposite sides of the hand as-in the FIG. 1embodiment. Likewise, a linearizer 52 is connected between the band-passfilter 42 and the synchronous detector 44.

[0049] The compensation for non-linearity can also be effecteddigitally, in which event it can conveniently take place in themicroprocessor 46.

[0050] Thirdly, the system 10.2 is provided with an auto calibrationbutton 54 which is connected to an input of the microprocessor 46. Itwill be understood that the switch button 54 could also be in the formof a touch pad. When the switch button 54 is activated by means of theoperator's right hand R, the microprocessor will perform a calibrationfunction, correlating the position of the operator's right hand R andthe cursor position on the computer screen 13. This is possible becausethe operator's right hand, when activating the switch button 54, will ofnecessity be in a known position in the X-Y plane.

1-13. (Cancelled)
 14. A position input device comprising: an oscillatorthat generates an oscillating injection signal for coupling to a firstbody part of a human body; a first input operable to receive a firstposition signal from a first position sensing electrode that provides afirst signal indicative of distance of the first position sensingelectrode from a second body part in a non-contacting manner; a secondinput operable to receive a second position signal from a secondposition sensing electrode that provides a second signal indicative ofdistance of the second position sensing electrode from the second bodypart in a non-contacting manner, the first and second position sensingelectrodes being spaced from each other; a differential amplifier havingfirst and second differential inputs connected to the first and secondinputs to receive the first and second signals; a processing deviceconnected to the differential amplifier and operable to generate adistance signal based on evaluation of the first and second signals. 15.The position input device according to claim 14, wherein the distancesignal is received by a computer to control a cursor on a display. 16.The position input device according to claim 14, wherein the processingdevice includes an analog-to-digital converter (ADC) connected to thedifferential amplifier and a processor connected to the output of theADC.
 17. A position input device comprising: an oscillator thatgenerates an oscillating injection signal for coupling to a first bodypart of a human body; a first input operable to receive a positionsignal from a position sensing electrode that provides a signalindicative of distance of the position sensing electrode from a secondbody part in a non-contacting manner; a differential amplifier having afirst differential input connected to the first input to receive thesignal indicative of distance; and a processing device connected to thedifferential amplifier and operable to generate a distance signal basedon evaluation of the signal indicative of distance.
 18. The positioninput device according to claim 17, wherein the distance signal isreceived by a computer to control a cursor on a display.
 19. Theposition input device according to claim 17, wherein the processingdevice includes an analog-to-digital converter (ADC) connected to thedifferential amplifier and a processor connected to the output of theADC.
 20. An input device for controlling the position of a cursor on adisplay of a computer, the input device comprising: at least one firstposition-sensing electrode positioned near a fixed reference framedefining an imaginary input boundary, for sensing the strength of afield established about a movable body part of an operator in anon-contacting manner and thereby to provide a first control variablecorresponding to the position of the body part in the reference frame ina first direction; at least one second position-sensing electrodepositioned near the fixed reference frame and spaced from the at leastone first position-sensing electrode, for sensing the strength of thefield about the movable body part in a non-contacting manner and therebyto provide a second control variable corresponding to the position ofthe body part in the reference frame in a second direction; and acontrol circuit operative in response to the first and second controlvariables to position the cursor on the display screen in accordancewith the position of the body part in an active region defined by thereference frame; the cursor being positioned in response to the firstand second control variables by movement of the body part in the activeregion.
 21. The input device according to claim 20, further comprising asignal generator for generating an oscillating electrical signal, and aninjection electrode for injecting the electrical signal into the body ofthe operator so as to establish the field about the movable body part.22. The input device according to claim 21, further comprising akeyboard for entry of data and wherein the body part is one of the handsof the operator, and wherein the position-sensing electrodes are soarranged with respect to the keyboard that the operator can control theposition of the cursor by moving the one hand in a hovering manner overthe keyboard.
 23. The input device according to claim 22, wherein theinjection electrode is arranged to inject the electrical signal into thebody of the operator via the other hand of the operator.
 24. The inputdevice according to claim 22, further comprising one or more clickswitches for operation by the operator.
 25. The input device accordingto claim 24, wherein the click switch or switches are arranged to beoperated by the other hand of the operator.
 26. The input deviceaccording to claim 21, further comprising a pointing device and aselection device for enabling the operator to select either the pointingdevice or the input device for controlling the position of the cursor onthe display.